@ROM, I tried the tool heimdall under Windows® and uninstalled it very quickly. With Samsung’s ODIN3 I have collected best experiences.
Also under ODIN3 the immediate restart is known after flashing TWRP Recovery with file twrp-3.3.1-0-starlte.img.tar - and is deactivated there in the options.
The decisive point to success, however, is the complete manual switching off of the device:
This forcing to switch off the device causes TWRP Recovery to remain installed during my flash operations and not to be overwritten by StockROM Android Recovery again.
To switch off the S6 Edge I had done the following:
- press VOL (-) + POWER + HOME simultaneously - and wait patiently …
- but exactly at the moment when Samsung device goes out, i.e. the display turns black, …
- change from VOL (-) to VOL (+) and press all three buttons simultaneously {= VOL (+) + POWER + HOME} …
- the Samsung LOGO shows up
- wait a few seconds … until TWRP is displayed.